Tension control device



1944- v T. J. AAMLAND EI'AL 2,333,276

TENSION CONTROL DEVICE Filed March 21, 1941 3 Sheets-Sheet l INVENTORSTHO/7 d. lA'MLl NAT/M11062 H. (U/f 7/66 A 770 mvt Y 1944- T. .1. AAMLANDETAL 2,338,276

TENS ION CONTROL DEVICE Filed March 21, 1941 3 Sheets-Sheet 2 NV ENTORSM I'M? 3 A T ORNEY T. J. AAMLAND ETAL TENSION CONTROL DEVICE Jan. 4,1944.

3 Shee'ts-Sheet 3' Filed March 21, 1941 INVENTORS 7/905 (1 IIMAl/VflATTORNEY Patented Jan. 4, 1944 2,338,278 TENSION con'raor. nnvroa ThorJ. Aamland, Leonia, and Nathaniel 11. Cartiss, Clifton, N. 1., assignorsto United States Rubber Company, New York, N. Y., a corporation of NewJersey Application March 21, 1941, Serial No. 384,510

Claims. (Cl. 242 158) This invention relates to tension control devices,particularly but not exclusively adapted to be used in the braiding ofmetal strands or wires under high tension, for'example in braidingmachines shown in the patent to J. A. Muller, No. 2,197,111. Thisapplication is a continuation-inpart of our co-pending application,Serial No. 262,696, filed March 18, 1939, now abandoned.

Heretofore in tension control devices in general use it has been founddiflicult to maintain a predetermined substantially constant and uniformtension on a strand of thread, wire, or similar material, whileunwinding it from a carrying spool. The feeding of the strand from thespool to a knitting, weaving, braiding, sewing or like industrialmachine at a uniform, predetermined tension is. in many cases, verydesirable, but has not been obtainable using control devices of formerconstructions.

Various types of devices have been previously employed to control thetension in the strand taken from the spool or reel but it has not beenpossible with any of these devices to maintain the proper predeterminedand substantially uniform tension desired under all conditions ofoperation, and accordingly many diiilculties and undesirable conditionshave been encountered. When it was attempted to use such devices forsupplying a strand to industrial machines mnning at high, low andvarying speeds such objectionable conditions as overrunning of thespool, slackening, twisting and breaking of the strand, and unevennessor braiding, weaving, sewing, or knitting, or the like, of the articlebeing formed has occurred. Such conditions have also resulted inrequiring extra power in the operation of the machine and excessive wearand breakage in the parts thereof and parts of the tension controldevices. Some of these devices have operated for certain conditions, forexample, when a spool is substantially full or when the strand takentherefrom is perpendicular to the axis of the spool, but have failedmaterially to give anything like the same results when these conditionshave beenvaried.

Our invention has largely eliminated the above objections anddiiliculties since we have provided a device that is substantiallyconstant and uniform in its operation, allowing the strand to be takenfrom the spool at substantially uniform tension and at any predeterminedvalue desired regardless of the amount of material remaining upon thespool, the speed at which the strand is taken, or the angle of thestrand being fed from the 8900 Our invention comprises a constanttension control device in conjunction with a spool or reel so arrangedand constructed as to be responsive to a predeterminedtension in astrand being unreeled therefrom, to yield and allow unwinding of thestrand from the spool when the desired tension has been exerted on thestrand, and to hold the spool against rotational movement at all timesexcept when such predetermined tension exists in the strand. Thispredetermined tension is governed by the strength of a particular springemployed in the device and the device is so arranged that it isimmediately and instantaneously responsive to variations 01' tensionthat may oc our. The unreeling action continues as long as suflicientpull is maintained on the strand but should this pull be lessened, evena very slight amount, our device is immediately responsive to retard theunreeling action or to prevent further feeding of the strand therefromas may be required to maintain a constant tension.

It will be seen from an inspection of the accompanying drawings and fromthe description that follows that our device is not only effective inits operation, constant and direct in its response to predeterminedtension, but also simple in operation, economical in construction, andcomposed of parts easily and readily adjustable and replaceable.

In the drawings:

Fig. 1 shows a front elevational view of our invention with a spoolpartly broken away and exposing a strand of material thereon and a brakeshoe in engagement with the spool rim.

Fig. 2 is a view of the device taken substantially along the line 2-2 ofFig. 1.

Fig. 3 is a side elevation of our preferred brake shoe.

Fig. 4 is a plan view of the brake shoe shown in Fig. 3.

Fig. 5 is a side elevation of the device shown in Fig. 1 but having thelower part thereof broken away along line 5-5 of Fig. 1, and the strandof the flexible material removed to more clearly show parts of thedevice.

Fig. 6 is a top plan view of the structure shown in Fig. 1 but havingthe strand of flexible ma terial removed therefrom. A

Fig. '7 is a partial front elevational view of our invention takenapproximately along the line 1-1 of Fig. 6 but showing parts of thecontrol mechanism in place thereon and in an inoperative position.

Fig. 8 is a partial elevational view, somewhat reduced and partly insection, of a modified form of our invention showing a brake controlledrotatable disc in engagement with a removable spool.

Fig. 9. is a side elevation of a modified form of brake shoe having aneccentrically located bore. Fig. 10 is a side elevation of anothermodified form of brake shoe, and

Fig. 11 is a plan view similar to Fig. 2 showing the brake shoe of Fig.10, and mounting means therefor, substituted for the brake shoe shown inFigs. 3 and 4 and its mounting means.

I As illustrated herein our device comprises a frame having the base I,upstanding support standard 2, and top cross member 3. Carried bysupport standard 2 is a fixed, laterally projecting spool supporting arm4, on which a spool 5 may be rotatably mounted. Positioned above an endflange 5a of the spool is a fixed shaft 6 on which the swinging lever Iis pivoted at its lower end. The lever I has a laterally projectingeccentric circular boss or cam 8 on which the brake shoe 9 is supportedin position to be moved into and out of contact with the periphery ofspool end flange 5a.

The upper end of lever I is secured by pin I to the lower end of a rodII, the upper end of which projects through a slot l2 extendingvertically through the frame top cross member 3. As illustrated in Fig.the upper end of lever l is bifurcated for the reception of the lowerend of rod ll.

Encircling rod II is a compression spring l3 which has at its upper endthe washer l4 which bears against the downwardly projecting edge l4a ofa contact member l5, centrally bored for the passage of rod I I. securedto top cross frame member 3 around slot I2. The lower end of spring l3abuts against shoulder l6 formed by the enlargement of the lower end ofrod l l.

The pulley I1 is mounted for free rotation on an enlarged centralportion of shaft I! fixedly secured in any suitable manner in top crossframe member 3, and is provided with a downwardly extending guidebracket l9 which fits over the threaded end portion of shaft I8 and isheld against the shoulder 18a of the enlarged portion by a nut lBa.

A similar pulley 20 is mounted for free rotation on an enlarged centralportion of a shaft 2|, which is fixed in any suitable way to lever 1below its connection to rod II, and is provided with an upwardlyextending guide bracket 22 which fits over the threaded end portion ofshaft 2| and is held against the shoulder Ila of the enlarged centralportion by a nut 22a.

The guide brackets I8 and 22 are provided with laterally extending armscurved back to form guides, and arranged to overlie the central portionof the bracket as best seen in Figs. 1 and 11. These arms are soarranged that the strand of material S can easily be slipped into eitherslot formed thereby and when so positioned will remain securely in placeas long as any tension is maintained in the strand S.

As shown in Fig. 1, a strand S of flexible material such as thread,wire, or the like, is led from spool 5, over pulley ll around pulley 20and again upwardly through the guide slot 25, extending verticallythrough the frame top crossv member 3, to an external location where itis to be utilized for any general industrial purpose. It will beunderstood that any tension on strand S will tend to rotate lever I in aclockwise direction, against the force of spring l3 which tends torotate lever l in a counterclockwise direction.

Various strength springs or additional washers about the rod H at theends of the spring may be utilized to obtain various degrees ofpressureand accordingly various amounts of resistance may be offered to thestrand being unreeled from our device.

The spring I3 is positioned with respect to lever I at an obtuse anglesuch that the length of the force arm through which the force of thespring is transmitted to the braking element varies substantially ininverse proportion to the force exerted by the spring throughout therange of angular movement of lever 1.

Thus the spring l3 exerts a constant moment of force tending to rotatethe lever 1 counterclockwise.

As illustrated in Figs. 3 and 4, the brake shoe 9 is a rectangularmember having four similar concave contact surfaces So, each of which iscurved along an arc concentric with the periphery of the end flange 5aof spool 5. Each contact surface 8a of brake shoe 9 is also groovedlongitudinally to fit over, the laterally rounded edge of end flange 5aof the spool. The brake shoe 9 has a central bore c adapted to fitloosely over the periphery 8a. of cam member 8 on lever 1. Asillustrated herein (Fig. l), cam member 8 is eccentrically mounted sothat its leading edge m, as it rotates in a clockwise manner, raisesbrake shoe 9 out of contact with the end flange 5a of the spool, and asit rotates in a counterclockwise direction it lowers the selectedcontact surface 9a of the brake shoe into contact with the end flangeEd. I

If desired the contact surfaces 8a may be spaced at different distancesfrom the bore 0 to compensate for wear on the peripheral surface offlange 6a. Thus, for example, if the surface of spool flange 5a becameworn, and lever arm I dropped too far as a result, the brake shoe couldbe turned so that a contact surface in spaced farther from bore 0 thanthe contact surface previously employed, would rest on flange 5a, thusmaintaining a more or less uniform setting for the spring.

The spool 5 is rotatably and removably mounted upon shaft 4, which ifirmly secured in a boss formed in the intermediate portion of theupstanding support arm 3, so that the spool may be removed laterallytherefrom whenever it is desired to replace it by another. A lock-bar 26is positioned between bifurcated ends 21 of the shaft 4 and is retainedin place by a pin 28 extending through said bifurcated ends and througha key hole slot 29 in lock-bar 26, A spring actuated plunger 30 isarranged in the shaft 4 and is adapted to bear against the lock-bar 26and hold it either in a vertical operative or an extended horizontalinoperative position, the latter position being shown by a dash and dotline in Fig. 5. The mere sliding of the lock-bar upwardly from its fullline vertical position, shown in Fig. 5, and then swinging it to itsextended dash and dot line position, allows the spool 5 to be easilyslipped over the lock-bar and onto the shaft 4. The lock-bar is thenreturned to a full line position and as such serves to prevent.

the spool from moving ofl the shaft 4. The

plunger 30 tends to maintain the lock-bar in When it is desired toremove a spool from the shaft 4 and replace it by another, it is onlynecessary. as best seen in Figs. 1 and 'I, to move the lock-bar to itsextended position by means of the curved end of work tool 32 and theninsert the straight end of the work tool into the bore b in the lever Iand rotate the lever about the shaft 3 against the action of the springI3. The lever 1 and shoe 3 will be moved from the operative positionshown in Fig. 1 to the inoperative position shown in Fig. 7. Thisrotation of lever I raises the brake shoe 3 and lifts the entire contactface So away from peripheral edge or flange a of the spool 8,asindicated in Fig. 'I, so that the spool is free therefrom and may bemoved laterally along and off the shaft 4.

The slot I2 is shaped to allow the swinging lever I and rod II to bemoved past the dead center position, and to stop the movement just afterthe dead center position has been passed. The spring then holdsregulating device in the inoperative position shown in Fig. 'l.

The flanges 5a of the spool 5 are formed of case hardened steel or othersuitable material to stand the abrasive wear occurring between them andthe brake shoe 9 while the device is in operation. The brake shoe 3 issimilarly constructed of case hardened steel or like material in orderto also resist excessive wear that would otherwise occur between theseparts. A stop member 33 is threaded or otherwise fastened into the sideof the frame member 2 and is provided to limit the downward swingingmovement of the lever I. When the spool 5 is in its operative positionupon the shaft 4 the peripheral edge or flange So will limit thedownward swinging movement of the lever I by frictionally engaging thebrake shoe 3. But should the lever I be moved downwardly when the spoolinot in its proper place upon the shaft to limit this movement, the stopmember 33 is effective to provide an abutment for the device and preventthe upper end, Ila, of the guide rod II from becoming disengaged fromguide slot l2 as will be apparent. from Fig. 7. If it is desired toremove the regulating device, the stop 33 maybe removed and the spool 5removed to permit the arm I to rotate counter-clockwise until the end ofthe rod II is withdrawn from the slot l2. All of the parts may then beslid axially from the shaft 6.

The operation of our device is as follows:

When it is desired to place the device in operation the spool of thread,wire or like material is moved onto the shaft 4 whilethe look-bar isextended and the lever 'I and brake shoe 3 are in inoperative position.The lock-bar 26 i then moved to its vertical position and lever 1 andbrake 3 are swung to their operative position at which time the flangesof the brake shoe 3 will straddle the peripheral edge of a flange 5a ofthe spool 5 and retain the spool against lateral movement along theshaft 4. The pressure exerted downwardly upon the swinging lever I bythe spring I3 transmits a predetermined pressure, through cam 3, to thebrake shoe 9 in contact with the flange 5a of the spool 5, and therebyholds the spool against rotational movement. As shown in Fig. 1, thefree end of the strand S is passed upwardly through one slot in theguide bracket I 9, over the pulley I1 and then downwardly through theoppostie slot in the guide bracket I3. It is then passed downwardlythrough the slot in one side of the guide bracket 22, around the pulley20 and hence upwardly through the other slot in the bracket 22 andthrough the guide or eye member 25 in the top frame member 3, from whichit extends to the place or machine where it is to be utilized. Thu thepulley 23 serves to transmit to lever arm I the force of tension onstrand 8.

As long asthe brake shoe 3 is in contact with the flange of the spool,the braking force equals the moment of force of the spring I3 minu themoment of tension in the strand acting at the center of the shaft 2| ofthe pulley 20. Since the moment of the spring I3 is constant, thebraking force varies inversely with the tension in the strand. As thetension increases the braking force decreases until it reaches a valuewhich permits the spool to rotate. The strand then unwinds. tension ofthe strand (for example, friction or binding of the strand as it isbeing unwound from the spool) immediately reduces the braking force, andany, tendency to reduce the tension (for example by too free running ofthe spool will immediately increase the braking force). Thus a balancedcondition will be maintained and the braking force will continuously andautomatically be adjusted to maintain a constant tension in the strand.It is only necessary that the strand of material on the spool be held orsecured against slipping relative to the spool in order that our devicefunction properly. Any common manner or means of preventing suchslipping action from occurring will be satisfactory for the operation ofour device.

In Fig. 8 is shown a modified form of our invention arranged with thebrake shoe 9 operating against a rotating disc 35 which is similar inform to one of the flanges 5a of the spool 5 of our preferredembodiment, but is operatively mounted upon the same shaft 36 whichsupports the spool. The shaft 36 is removably secured in support 2 inany well known manner and is provided with a shoulder 31 to rotatablyretain the disc 35 in place thereon. In such a construction it will onlybe necessary to provide the disc with suitable clutch elements, such asa laterally extending finger 38, to engage an aperture formed intheflange of any conventional spool 39 placed upon the shaft 36. Thus,an operative drive between the spool and the rotating disc is formedwhich is simple in construction and readily allows the removal of saidspool from the shaft. Such an arrangement would not limit the controldevice to any particular size or type of spool but would be useful forany conventional spool as will be readily apparent. It would only benecessary for such a spool to have formed therein apertures foralignment with the finger 38 extending laterally from the rotating disc.

The operation of our device occurs under substantially uniformconditions regardles of whether we employ such a rotating disc 35, inconjunction with the brake shoe 9, or the flange 5a of the spool 5 inconjunction with such brake shoe.

In Figs. 9 and 11 a modified brake shoe 40 and supporting means thereforare shown. In this embodiment of the invention. a swinging lever or arm4| is used instead of lever I, and is mounted on the outer end of sleeve42 which is rotatably supported on shaft 43, which, like arm 2|, isfixedly supported by frame member 2. Brake shoe 40 is threadedly engagedon the inner end of shaft 43. The arm ll and brake shoe 40 are heldtogether by the clamping action of shoulder 4311, on .the outer end ofthe sleeve 42, when the inner end thereof is in threaded engagement Anytendency to increase the with the brake shoe 40 as clearly shown in Fig.11.

The swinging arm 4| is provided with means to prevent relative rotationbetween it and the brake shoe 40. For this purpose a pin P extendslaterally through the arm 4| and has its end arranged and adapted toengage in one of a series of apertures 44 upon a side of the brake shoe40.

This arrangement is such that when the swingcondition thereof isproduced and the brake shoe may be reversed and an opposite edge used ina like manner for braking purposes when considerable wear hasdevelopedalong one edge. This brake shoe 40 is eccentrically bored, thus formingan eccentric cam, having a groove 46 in its 7 elements.

peripheral edge or rim. This groove forms flanges 41 at either sidethereof and these are cut away or beveled at portions adjacent thecenter of oscillation of the cam, as indicated by the reference numerals48, Fig. 9.

The outer end of the sleeve 42 is squared as shown at 49 so that thesleeve may be easily gripped while the threaded inner portion 50 isbeing turned into threads of the brake shoe 40. It will be seen byinspection of Fig. 11 that when the sleeve 42, swinging arm 4|, brakeshoe 40 and pin P have been fitted together a rigid but readilydetachable and adjustable assembly is effected.

The bore 52, illustrated in the swinging lever 4| of Fig. 11, like thebore b of Fig. 1, is for receiving the end of tool 32 by which lever 4|and brake shoe 40 may be swung to inoperative position.

In Fig. we show another modified brake shoe 53 which may be employed inplace of the brake shoe previously described. The brake shoe 53 iscircular and has a peripheral edge 54 which is concentrically arrangedrelative to the center of oscillation of the shoe. This edge 54preferably although not necessarily, has a groove 55 formed therein forcentering and retaining the flange 5a of the spool 5 in placetherebeneath.

Either face 56 of brake shoe 53 may be used to engage the flange 5a ofthe spoo1 5 for braking 5 purposes. A series of holes 51 are provided inone side of the brake shoe to allow relative adjustment between the shoeand the swinging arm 4| (Fig. 11) by detachable engagement with the endof the pin P carried in the swinging lever 4| (Fig. 11). A similarseries of holes (not shown) are located in the opposite side of thebrake shoe 50 and allow for similar adjustment of the shoe when it isbeing used in its reversed position.

When this brake shoe 5!! is being used upon our device a small area ofcontact is formed between the face 53 and the flange 5a. When wear hasresulted at this area of contact, the shoe may be readjusted and it willbe seen that the area of contact remains substantially constant eventhough a considerable amount of wear may have resulted. The two seriesof holes on the opposite sides of the brake shoe 50 make it possible toutilize a large amount of the peripheral edge of the brake shoe forbraking purposes by merely place this shoe by another shoe of similarconstruction. Even after considerable wear has resulted along the edgeof thisbrake shoe the braking resistance oifered by the device may bemaintained substantially constant by a mere readjustment of the shoerelative to the swinging lever 4|.

Throughout the description reference has been made, for the sake ofbrevity and avoiding repetition,-generally to the term strand inconnection with our invention. However, it should be clearly understoodthat the word strand appearing herein is intended in its generic senseand that our invention is equally useful and intended to serve inconjunction with various materials such as thread, yarn, wire, cord,tape and the like either in single filament form or when twisted orbraided together as composite flexible It is only necessary when acertain material is to be used to proportion the parts of our controldevice for the particular characteristics of the material and such canbe readily done without involving more than changes in size or shape ofthe parts described herein and without departing from the spirit of ourinvention.

While we have described certain present preferred embodiments of ourinvention, it will be readily apparent to those skilled in the art, thatcertain changes may be made therein without departing from the essencethereof or the spirit and scope of the appended claims.

Having thus described our invention, what we claim and desired toprotect by Letters Patent is:

1. In a tension control device for a strand of flexible materialcomprising a support, a spool from which a strand of flexible materialis being unwound mounted on said supp rt, a lever arm pivoted to saidsupport adjacent said spool, means tending to rotate said lever arm inone direction around its pivot, means responsive to tension in thestrand being unwound from said spool for opposing said first mentionedmeans, a braking element having a number of contact surfaces ofsubstantial length each of which is shaped so as to contact said spoolthroughout its entire length, said braking element being movable intoand out of contact with said spool by a cam member mounted on said leverarm.

2. A tension control device comprising a support, a spool rotatablymounted thereon and adapted to carry a strand of flexible material, andcontrol means carried by said support comprising a movably mounted brakeelement for normally holding said spool against rotational movement andspring means for normally urging said brake element into holdingposition, said control means being normally responsive to predeterminedtension in said strand to release said brake element and allow saidspool to rotate under the influence of said predetermined tension, andalso being responsive to the release of said predetermined tension inthe strand to hold said spool against rotational movement, said brakeelement being movable from its holding position to an inoperativeposition, said spring means being automatically operable to releasablyretain the brake element in said last named position.

3. A tension control device comprising a support, a spool rotatablymounted thereon and adapted to carry a strand of flexible material, a

pulley and a guide mounted upon said support and arranged to receive thestrand. extending from said spool, control means pivotally carried bysaid support comprising brake means normally holding said spool againstrotational movement and having a braking surface, a second pulley and alever for supporting said pulley, said lever being connected to saidbrake element for controlling the angular position thereof, and a springurging said lever and said brake means into holding position, said guideand pulleys being so arranged that an elongated loop is formed in thestrand extending from the spool successively around the first and secondpulleys and through said guide, and being so positioned that said loopextends in a general direction which is substantially parallel to saidspring and is at a substantial obtuse angle relative to said lever, saidbraking surface normally engaging said spool at a substantially constantpredetermined location, whereby said lever and brake means areresponsive to predetermined uniform tension in the loop to release saidspool to rotate under the influence of the tension in the strand, saidcontrol means being pivotally movable to an inoperative position so asto retract said brake element from said spool, said spring means beingautomatically operable to retain said control means in said retractedposition.

4. A tension control device comprising a sup porting frame having anaperture formed in an end portion thereof, a shaft and a pivot carriedby said frame in spaced relation to said end portion, a spool rotatablymounted upon said shaft and adapted to carry a strand of flexiblematerial, means upon said pivot for controlling the rotation of saidspool, said means comprising a brake element normally in engagement withsaid spool and a control arm secured to said brake element for pivotalmovement therewith, said control means also comprising a guide rodhingedly connected to said arm at a point remote from said pivot andhaving an end thereof slidably fitting within the aperture in saidframe, a coil sprin surrounding said rod and having its opposite ends inengagement with the end portion of the frame and with said rod so as toforce said brake element into engagement with said spool, a pulley uponsaid arm remote from said pivot and adapted to be actuated by the strandextending from said spool, said control means being normally responsiveto predetermined tension in said strand for releasing said brake andallowing the spool to rotate, said control means being swingable whensaid spool is removed from said shaft into an inoperative positionretracting said rod from said aperture and thus allowing the controlmeans to be moved axially as a unit and disengaged from said pivot.

5. A tension control device comprising a supporting frame having anaperture formed in an end'portion thereof, a shaft and a pivot carriedby said frame in spaced relation to said end portion, a spool rotatablymounted upon said shaft and adapted to carry a strand of flexiblematerial, means swingably carried by said pivot for holding said spoolagainst rotational movement and for controlling the rotation thereof,said means comprising a semi-circular brake element concentricallymounted for movement about said pivot and having a contacting surfacedisposed upon the periphery-thereof and normally in engagement with saidspool, said means also comprising a control arm releasably secured toand holding position, said control means being nor--.

mally responsive to predetermined tension in the strand extending fromsaid spool for releasing said brake element, said contacting surfaceupon said semi-circular brake element remaining at a constant distancefrom said pivot regardless of wearing away of the brake element duringoperation of said device:

6. Apparatus for maintaining a constant tension in a strand of flexiblematerial comprising in combination means for rotatably supporting a coilof flexible strand, a brake having a brake surface and being ofsubstantial thickness in a direction normal to said surface, said brakebeing movable to place the braking surface in a predetermined positionto prevent rotation of the coil, control means exerting a predeterminedforce urging the brake to braking position, ,the' control meansincluding a pivoted brake arm supporting the brake and a spring urgingthe brake arm to braking position, the angle of action of the spring,length of brake arm and distortion of the spring being so related as tomaintain said force substantially constant throughout movement of thebrake arm due to wear of the brake, and means responsive to the tensionin a strand being un- 'wound from said coil for urging the brake in theopposite direction against the force of the control means.

7. Apparatus for maintaining a constant tensurface is in brakingposition regardless of change of position of the brake arm due to wearbetween the brake and spool and means responsive to the tension in astrand being unwound from said spool for urging the brake against theforce of the control means.

8. Apparatus for maintaining a constant tension in a strand of flexiblematerial comprising in combination a rotatable member adapted to beassociated with a coil of flexible strand, a brake having a brakingsurface and being of substantial thickness in a direction normal tosaid' surface, control means exerting a. predetermined constant forceurging the brake against the member, the control means including apivoted brake arm supporting the brake and a spring urging the brake armto braking position, the angle of action of the spring, length of brakearm and distortion of the spring being so related as to exert saidpredetermined force when the surface is in contact with the member,regardless of wear between the surface and the member, and meansresponsive to the tension in a strand being unwound from said coil forurging the brake against the force of the control means.

9. Apparatus for maintaining a constant tensiori in a strand of flexiblematerial comprising in combination means for rotatably supporting a coilor flexible strand, a brake and a rotatable brake arm adapted to placethe surface of the brake in a predetermined position to prevent rotationof the coil, control means including a spring exerting a predeterminedconstant moment tending to rotate the arm in one direction to place :thebrake surface in said predetermined posiin combination means forrotatably supporting a coil or flexible strand, a-brake and a rotatablebrake arm adapted to place the surface of the brake in a predeterminedposition to prevent rotation of the coil, a pivot on the brake arm, aspring acting on the pivot to urge the brake to braking position, theangle of action of the spring with the brake arm, the length of thebrake arm and the distortion of the spring being so related that as theforce exerted by the spring decreases due to'movement of the brake theeiiective length of the lever arm through which the spring acts torotate the brake arm increases proportionately preserving a constantmoment tending to rotate the brake arm regardless of the angularposition of the brake arm, and means responsive to the tension on astrand being unwound from said coil for urging the brake against ,theforce or the spring.

THOR J. AAMLAND. NATHANIEL H. CURTISS.

